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International Journal of Engineering and Technical Research (IJETR)
ISSN: 2321-0869 (O) 2454-4698 (P) Volume-7, Issue-7, July 2017

A Review on Microstrip Patch Antenna and its
Miniaturisation Techniques
Sumit Gupta, Toolika Srivastava

Abstract— Microstrip patch antenna (MPA) has been widely
in use since past three decades. The MPA consists of a metallic
patch on the dielectric substrate over a metallic ground plane
and is quite easy to design and fabricate. The minimum
dimension of earlier MPA was half of wavelength which was
very large for some communication devices; but recent some
researchers have developed new standard for reducing the size
of patch antenna. Many miniaturisation techniques have been
introduced by researchers during recent years such as material
loading, reshaping of antenna, shorting and folding, introducing
slots and defects in the ground plane and the use of Meta
materials. The major features and drawbacks of each of these
approaches have been highlighted in this paper along their
effects on antenna performance. This paper will provide better
understanding for new researchers.

Monopole and dipole Antenna and planer inverted F shaped
antenna (PIFA).[19]
As it is known that other parts of the communication devices
are difficult to design and smaller in size but in case of
antenna designing it is quite simpler because the length of
antenna is the order of half of the wavelength of that
frequency. Although there are so many theories given for
designing the small size antenna by increasing their
bandwidth and Gain but there are limited theories for the
miniaturisation of Antenna structures.
In this paper, it is presented how antenna size can be
miniaturised with their performance, their effects and their
drawbacks.

Index Terms—About four key words or phrases in
alphabetical order, separated by commas.

II. PATCH ANTENNA
A micro strip antenna which is generally referred as Printed
antenna is an antenna that is fabricated using micro strip
techniques on a printed circuit board (PCB). These antennas
generally used for the microwave frequencies. Micro strip
patch antenna is a simplest form consist of a sandwich of two
parallel conducting layer separated by a single thin dielectric
substrate. Micro strip patch antenna are formed by
overlapping two metallic plates, first is the large than the
other, with a dielectric sheet in the middle. A micro strip patch
antennas in its form consists of a metallic radiating patch on
one side of dielectric substrate, which has a ground plane on
other side. The dielectric constant should be low, so as to
enhance the fringe field which account for radiation. Other
performance and design requirement may dielectric constants
may be greater than five. Design procedure of antenna is very
simple [1 and 20]. It can easily be connected with the
electronic devices and can also be used with the available
substrate materials for the fabrication purpose.

I. INTRODUCTION
At present, Wireless communication devices generally used
are Global Positioning System (GPS), Radio Frequency
Identification (RFID) system, AM and FM Radios, Mobile
phones, Laptops etc. The Antenna is a vital part of these
devices. Therefore, there is a requirement of such antenna
which is easy to design and fabricate; also due to compactness
in size of wireless devices the antenna required for these
devices should be compact.
Among the various antennas, the Microstrip Patch Antenna is
best suited for the entire requirement. Therefore it is very
popular among the researchers of this area. The main reasons
of its popularity are:
 It is a low profile antenna.
 Easy to design and fabricate.
 Easy to integrate with monolithic ICS.
 Easy to mount on any surface.
 It is easy to produce it in bulk.
 Low cost of this antenna makes it useful in daily life
communication devices.
This Antenna can be designed by using printed circuit
technology and was firstly presented in the 50s but it did not
attain good gain. After the 80s it has appeared with lots of
improved characteristics.
Micro strip Patch antenna (MPA) is one of the examples of
printed Antenna. The other example of printed antenna is

Sumit Gupta, M.tech Scholar, Department of Electronics and
Communication Engineering, Kanpur Institute of Technology,
Kanpur-208001, India
Toolika Srivastava,Assistant Professor, Department of Electronics and
Communication Engineering, Kanpur Institute of Technology,
Kanpur-208001, India

a). 3D view

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A Review on Microstrip Patch Antenna and its Miniaturisation Techniques
outer conductor is connected to the ground. [3] The
conducting strip is smaller in width as comparison to the patch
and this kind of feed arrangement has the advantage that the
feed can be etched on the same substrate to provide a planar
structure as shown in fig -3. but there is a limitation in both
excitation methods that they limit the bandwidth of MPA
[2,4]. There are alternative approaches like proximity coupled
and aperture coupled feeding techniques to minimize the
above problem.
b). Top and Side view
Fig-1 Microstrip Patch Antenna
In figure -1 the simple design of microstrip patch antenna
with their feed line is shown. It has already been discussed
that it is a very low profile Antenna so it can be easily used in
the global positioning system (GPS), laptops, tablets,
Personal digital assistants (PDAs) and so on.
An MPA can be analysed using the rectangular cavity model
in which there is a rectangular shaped cavity which is covered
with top and bottom of the conducting sheets referred as
(Perfect Electric Conductors) PECs. These are filled with the
dielectric substrate and their side walls work as a (Perfect
Magnetic Conductors) PMC and the radiation will occur
through the side walls of the cavity due to the leakage of field
lines and the resonance of these field lines can be calculated
by applying the boundary conditions on the cavity walls for
different modes of resonant frequency. [3]

Fig.4 Aperture feed [7]
These methods are called as indirect feeding of MPA and are
of very complex design and rarely used. They provide the
wider operating bandwidth.

IV. MINIATURISATION OF PATCH ANTENNA:
Miniaturisation of patch antenna is a very important factor
for the designing of Antenna but lowering the size of Antenna
results in lowering of bandwidth and reduction in gain [5] but
after several researches it has been concluded that if a small
antenna is enclosed in a sphere of radius “a” then quality
factor is given byQ = (1/ka) + (1/ka)3
where k is wave number. By this evidence, if quality factor is
increased then efficiency and gain will also be increased but
bandwidth will be reduced.
There are many basic techniques to Miniaturise the antenna in
which some are following:-

The resonant frequency can be obtained using the formula –
fr (mnp)=
h=height of substrate
l=length of patch
w=width of patch
µ=permeability of material
ɛ=permittivity of material

III. EXCITATION METHODS OF MPA

V. USE OF METAMATERIALS
Metamaterials are those materials which are artificially
designed to provide material properties. These materials are
not commercially available, metamaterials are desined in a
such a way that it has near zero value permittivity or negative
permittivity or permeability ; or it has simultaneous negative
permittivity and permeability.
A material having only negative permittivity is called epsilon
negative(ENG),where as only negative permittivity is called
µ-negative(MNG)materials. And finally a material which has
both negative permittivity and permeability is called as
double negative(DNG).
These materials are widely used in RF, microwaves and
photonics devices to achieve interesting properties. The
concepts of metamaterials and their structures have also been
used to design various antennas to enhance their
characteristics like-gain, efficiency etc.
For example the design of rectangular microstrip patch
antenna with DNG metamaterial provides tetra band
resonance falling between 4GHz and 9GHz. [14-15]

An MPA can be excited through different ways. The
excitation methods of MPA are co-axial feed excitation,
micro strip feed excitation, and transmission line feed
excitation [3]. The simplest Feeding technique is used for
MPA is transmission line feeding excitation in which a
conducting strip is attached to the edge of patch as shown in
fig-2.

Fig.2Transmission Line
Feed[7]

Fig.3 Co-axial Line Feed [7]

In other techniques like Coaxial Feed Line Method, the inner
conductor of a co axial line is connected to the patch while the

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International Journal of Engineering and Technical Research (IJETR)
ISSN: 2321-0869 (O) 2454-4698 (P) Volume-7, Issue-7, July 2017
VI. INTRODUCTION OF DIFFERENT SLOTS
An MPA can also be miniaturised by using different types of
Shapes and slots on the patch antenna that creates large
electrical length [6] and smaller in size but reduces the
bandwidth of antenna.
Modification is done by using different slots in the microstrip
antenna ,if the slots are properly designed then it increases the
electrical length for the propagation of the current, and also
reduces the resonant frequency .After several studies it is
found that a single slot of 1mm width reduces size and its
resonant frequency. Initially MPA will be resonated at 2.87
GHz with slot after introducing a slot the MPA will be
resonated at 1.38GHz which represents 52% decrease. If 3
slots are introduced the resultant antenna size is 50% decrease
and if multislot (4 slots) are introduced in the MPA then its
Bandwidth will be reduced to 26.92% from 27.62% and the
better return loss (-28dB) is obtained at 1.88 GHz.[10]
As already discussed in the previous lines that introducing
different slots reduces the resonant frequency as well size of
antenna .Further introducing a H-shaped patch (w=5mm;
L=26.33mm) shown in fig-5a ,additional 4 vertical slots
(L=10mm;w=5mm) shown in fig-5b ,four more horizontal
slots with (w=3mm;L=10mm) are added shown in fig-5d ,it
reduces the resonance frequency to 888MHz , 801 MHz,
680MHZ and 570MHz.[11-13]

Figure 6 Spiral shaped defected ground structure[8]
Further it is observed that a size reduction of 56.68% has been
achieved by taking out ‘I’ shaped slot from both patch and
ground ,results new antenna has return loss of -14.34 dB at
5.54GHz and -16.56dB at 6.27GHz while a conventional
antenna exhibits -3.90dB at 5.45 GHz and -5.27 dB at
7.00GHz.[9]

Figure 7 'I' Slot on patch and ground[9]

VIII. USE OF SHORTING PINS
In the recent times miniaturization of antenna is in demand. In
wireless devices, the antenna still remains a matter of concern
as regard to its size in an antenna it is desired that all antenna
parameters like polarisation, radiation pattern and input
impedance should be same. Therefore, short circuit microstrip
antennas are used because this antenna can realize same
resonant frequency and required half the size of standard
micro strip antenna.
The shorted microstrip antenna is constructed by short
circuiting the zero potential plane of an ordinary microstrip
antenna exited with a dominant mode. In physical manner this
short circuit may be complete by wrapping a copper strip
around the edge of antenna or it may be simulated by shorting
post. From the manufacturing point of view construction of
shorting post is much easier than wrapping of copper strip
around the edge.
For example in rectangular microstrip antenna if shorting post
is done at the centre line of patch then it produces two lowest
resonant frequencies with same polarisation. If this shorting is
done in circular antenna at the centre line of patch then it also
produces two resonant frequency one is linearly polarised
(occur at lower frequency )and other is circularly polarised
(occur at higher frequency),this will reduced the area with a
factor 5 at the lower frequency end.[16-18]

Figure 5 Notch modifications in H shaped antenna[11]
VII. DESIGN OF DEFECTED GROUND STRUCTURE
With the use of different discontinuities in microstrip lines
improves the performance of different passive circuits,
including size reduction of amplifiers, enhancements of filter
characteristics and the applications to suppress harmonics in
patch antenna.
Defected ground structure disturbs the current distribution on
ground plane. This disturbance creates some resonators which
will be added to main structure, but it has no unwanted
radiation from its ground. Hence it enhances the electrical
length of microstrip lines and disturbs the current distribution
across the patch, then the effective capacitance and
inductance of microstrip line increases and accordingly
microstrip patch antenna with Defected Ground structure
(DGS) has slow wave characteristics which leads to reduction
of antenna size.
For example with the introduction of a spiral structure as
Defected Microstrip Structure (DMS)
in order to shift
resonance frequency, results shift of resonant frequency occur
from 5.8GHz to 2.69 GHz. Since DMS presents a slow wave
structure so it has more discontinuities provides a longer
trajectory to the EM waves [8].

IX. CONCLUSION
This paper presents the various miniaturisation techniques for
the micro strip Patch antenna, the fundamentals and the
different points about the Antenna size, bandwidth and gain.

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A Review on Microstrip Patch Antenna and its Miniaturisation Techniques
The various methods used for the miniaturisation of the patch
antenna are use of Meta materials, introduction of different
slots, design of defected ground structure and use of shorted
pins. Some techniques used for this method provide higher
level of miniaturisation while some provide the lower level to
maintain its bandwidth, gain, and efficiency ratio. This paper
also defines about the feeding methods of MPA and generally
uses direct feeding which included transmission line, coaxial
line feeding and indirect feeding that includes aperture
feeding.
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[3] Balanis, C.A.: ‘Antenna theory: analysis and design’ (John Wiley &
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[4] Lee, K., Tong, K.: ‘Microstrip patch antennas – basic characteristics and
somerecent advances’. Proc. of the IEEE, 2012, vol. 100, no. 7, pp.
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[5] Wheeler, H.A.: ‘Fundamental limitations of small antenna’, Proc. IRE,
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[6] Herscovici, N., Osorio, M.F., Peixeiro, C.: ‘Miniaturization of
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International Journal of Emerging Technology and advanced
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[14] Maryam Rahimi, Ferdows B. Zarrabi, RaheleAhmadian, Zahra
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[16] R. Porath, “Theory of miniaturized shorting-post microstrip
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No. 1, pp. 41-47, 2000.
[17] [2] M. Sanad, “Effect of the shorting posts on short circuit microstrip
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[18] Volakis, J.L., Chen, C., Fujimoto, K.: ‘Small antennas:
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[20] Khan Umar Muhammad, Sharavi Said Mohammad and Mitra Raj
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;A
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